Thermally developable light sensitive material

ABSTRACT

IN A THERMALLY DEVELOPABLE LIGHT-SENSITIVE PAPER COMPOSED OF A SILVER SALT OF BENZOTRIAZOLE, A LIGHT-SENSITIVE SILVER HALIDE, A REDUCING AGENT, SUCH AS, HYDROQUINONE AND AN ORGANIC ACID, SUCH AS, AN ALIPHATIC MONOCARBOXYLIC ACID, THE PRESERVABILITY OF IMAGES CAN BE IMPROVED BY USING 1-ASCRONIC ACID, ITS ESTERS, FUROIN, BENZOIN DIHYDROXY ACETONE, ETC., AS A REDUCING AGENT. ACCORDING TO THE PAPER USED, A NEGATIVE AND A POSITIVE COPY CAN BE OBTAINED FROM THE SAME MATERIAL.

Int. (:1. 063a 1/02 U.S. Cl. 96-1141 4 Claims ABSTRACT OF THE DISCLOSURE In a thermally developable light-sensitive paper composed of a silver salt of benzotriazole, a light-sensitive silver halide, a reducing agent, such as, hydroquinone and an organic acid, such as, an aliphatic monocarboxylic acid, the preservability of images can be improved by using l-ascrobic acid, its esters, furoin, benzoin, dihydroxy acetone, etc., as a reducing agent. According to the paper used, a negative and a positive copy can be obtained from the same material.

This is a continuation of application Ser. No. 643,828, filed June 6, 1967, now abandoned.

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a light-sensitive element and more particularly to light-sensitive elements capable of forming images in response to heating.

Description of the Prior Art In general, as light-sensitive elements, a photographic light-sensitive element in which a silver halide is used has been most Widely employed, since such a photographic silver halide light-sensitive element has excellent sensitivity and gradation, as compared with electrophotographic light-sensitive elements and other photographic light-sensitive elements. However, there are certain difficulties inherent in such photographic silver halide lightsensitive elements. For example, the light-sensitive element must be developed in a solution, after exposure, and the developed light-sensitive element must then be subjected to several processing steps in order to prevent the developed image from becoming discolored or faded and also to prevent the background thereof from being blackened. The latter processing steps are generally termed stopping, fixing and stabilizing in conventional photographic terminology. Therefore, it is very desirable, from the point of view of simplicity of processing, to obtain an image by a dry developing method and to provide a permanent image, while omitting fixing and other usual processes.

In an attempt to efiect such a method, various efforts have hitherto been made. One such eliort comprises an attempt, in silver halide photography, in which development and fixing are conducted in a single processing step. Such a process is called a mono-bath developing and fixing process, and is disclosed in US. Pat. 2,875,048; British Pat. 954,453; and German Pat. 1,163,142. Another attempt of the prior art is one in which the wet type processing of conventional silver halide photography is conducted in a dry manner. This is disclosed, for example, in German Pat. 1,174,159 and British Pats. 943,476 and 951,644. Still another attempt is one in which a silver salt compound, other than silver halide, is used. For

nited States Patent 3,827,889 Patented Aug. 6, 1974 example, such a method is disclosed in US. 3,152,904; Belgian Pat. 663,112, and our copending US. application No. 617,498, filed Feb. 21, 1967.

The present invention is concerned with the last-mentioned attempt. That is, a photographic light-sensitive element containing a combination of light-sensitive and reducible organic silver salts together with a slight amount of a light-sensitive silver salt.

Thus, an object of the present invention is to provide a novel photographic light-insensitive composition. .Another object of the present invention is to provide a novel image reproducing method. Still another obect of the invention is to provide light-sensitive materials which can provide both a negative and a positive copy of an original. Yet another object of the present invention is to provide a dry-type processing for conducting development by heating only, and without using any solutions in the developing process. A further object of the present invention is to provide a light-sensitive element which can provide an image stable to light and capable of being stored almost substantially without subjecting the developed image to fixing and other processing. Still other objects and advantages of the present invention will become apparent by the following detailed descriptions.

The inventors have previously invented a thermally developable light-sensitive element comprising a support bearing at least one layer containing substantially (a) a light-insensitive and reducible organic silver salt,

(b) an inorganic halide capable of forming a lightsensitive silver halide by reaction with the light-insensitive and reducible organic silver salt,

(c) a reducing agent, and

(d) a member selected from the group consisting of an organic acid and a salt thereof together with a suitable binder.

This thermally developable light-sensitive element could be developed by heating, after exposure, to provide an image having considerable light stability, without subjecting the developed image to processing, such as, fixation or stabilization.

The inventors have further investigated improving the above-mentioned thermally developable light-sensitive elements and found as the result thereof that the abovementioned objects of this invention can be achieved by using as the reducing agent contained in the thermally developable light-sensitive element a reducing material which loses its reducing property upon irradiation by ultraviolet rays, whereby the reducing agent is decomposed. The reducing agents which have hitherto been used for previous thermally developable light-sensitive elements are hydroquinone, methyl hydroquinone, phenyl hydroquinone, catechol, and the like, which are not decomposed by the irradiation of ultraviolet rays.

SUMMARY OF THE INVENTION Thus, the thermally developable light-sensitive element according to the present invention comprises a support hearing at least one layer containing (a) a light-insensitive and reducible organic silver salt, (b) a member selected from the group consisting of a silver halide and an inorganic halide capable of forming a light-sensitive silver salt by reaction with the organic silver salt (a), (c) a reducing agent capable of being decomposed by ultraviolet irradiation to lose its reducing property, and (d) a member selected from the group consistingof an organic acid and a salt thereof. 1

The reducing agent used in the present invention is a compound containing a group shown by the following formula:

OY OH or a compound containing a group shown by the following formula:

where Y represents a hydrogen atom or an acyl group. DETAILED DESCRIPTION OF THE INVENTION .Illustrative of suitable compounds useful as the reducing agent are the following:

l-ascorbic acid (I), l-ascorbyl mono-ester (II), l-ascorbyl diesters (III), and (IV), furoin (V), benzoin (VI), and dihydroxy acetones (VII).

These compounds are shown by the following formulas, respectively.

O b-n Lb on La. 8..

(311011 (anon IHzOH H20.CO.R

(I) (II) C=O C=O Tb-on b-ooon 0 i s-on L i-on L8. 8..

11000.3 bHorr HzO-CO.R CHzOCOR (III) (IV) 011 0 H OH o t 0/ Q-M-Q v11 OH 0 OH These compounds have the property of losing their thermal developability as a result of decomposition by ultraviolet irradiation.

These compounds have been known as antioxidants in color photography (for example, U.S. Pats. 2,401,713; 2,728,661 and 2,923,627 and British Pat. 922,550), as developing agents for liquid developers (for example, U.S. Pat. 2,688,549 and British Pat. 430,264), and as preservatives for liquid developers (for example, Phot. Sci. Tech., 2(2), 81 (1955)) but they have never been used in a thermally developable light-sensitive element.

Moreover, it should be noticed that the compounds shown below are unsuitable for this invention, since they are not decomposed by ultraviolet irradiation in spite of containing the group of -C(OH) =C(OH)- or CH(OH)-CO group. Namely, they are glycerine alde- 4 hyde (VIII), rhodizonic acid (IX) and tetrahydroxyquinone (X) shown by the following formulas, respectively:

vim) CHO-CHOH-CH2OH,

(1X) on 0 fl:() H H O-W O H 0 O H O I O H b b on When the reducing agent of this invention, capable of being decomposed and losing its thermal developability by ultraviolet irradiation, is used as a reducing agent for the thermally developable light-sensitive material described in the specification of our copending U.S. patent application Ser. No. 617,498, the light-sensitive material has better shelf life in storage, even under conditions of high temperature and high humidity, as compared with conventional thermally developable light-sensitive materials in which hydroquinone, etc., are used as the reducing agents. Also, when the material according to this invention is exposed imagewise to a tungsten lamp, in accordance with the usual manner in which a latent image formed thereby is developed, and the material is then placed in a lighted place resulting in the decomposition of the agent by the action of ultraviolet rays in the sunlight or the light from a fluorescent lamp to lose its reducing power, the image has better stability. Therefore, the light-sensitive material thus processed provides a very stable image which is no longer developed by heat or light exposure.

Instead of placing it in a light place, the light-sensitive material thus exposed and developed may be subjected to an ultraviolet irradiation to ensure forcibly the decomposition of the reducing agent. The amount of the ultraviolet exposure necessary to decompose the reducing agent is varied by the proportion of the reducing agent contained in the light-sensitive material, but, in the case of using a high pressure mercury lamp of 400 watts, it is sufficient to expose the developed light-sensitive material for 5 minutes at a distance of 10 cm. from the light source.

Moreover, such thermally developable light-sensitive material containing the reducing agent of the present invention can be used as an auto-positive material. That is, when the thermally developable light-sensitive material according to this invention is exposed to ultraviolet rays, through a transparent original, the reducing agent in the areas exposed to the ultraviolet is decomposed, but the reducing agent in the areas corresponding to the image, the unexposed areas, is not decomposed. Therefore, when the light-sensitive material exposed to ultraviolet rays through a transparent original is exposed to a tungsten lamp for a short time and heated, a stable developed direct positive image is obtained from an original, and hence, the light-sensitive material of this invention may be used as an auto-positive material.

As the light-insensitive silver salt used in this invention, there are illustrated silver salts of organic compounds having. an imino group, such as, the silver salt of benzotriazole, a silver salt of halogen-, methyland nitrosubstituted 'benzotriazole, and a silver salt of saccharin (O-sulfobenzoic acid imide) as described in our copending U.- S. application No. 617,498, and moreover, silver salts of organic compounds having a carboxylic group, such as, silver behenate.

The inorganic halide capable of forming a silver halide by reaction with the light-insensitive silver salt is a watersoluble or organic solvent-soluble compound as shown by the general formula MXn, wherein M represents hydrogen, ammonium or a metal, such as, strontinum, cadr'nium, zinc, tin, chromium, sodium, potassium, barium, iron, cesium, lanthanum, copper, calcium, nickel, magnesium, aluminum, antimony, gold, cobalt, mercury, lead, or beryllium; X represents ahalogen, such as, chlorine, iodine or bromine; and n represents the valency of M.

-. As the organic acid used in this invention, there are saturated aliphatic monocarboxylic acids having from 9 to 26 carbon atoms, such as, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, behenic acid, cerotic acid, and the like. Among them, those having from 12 to 22 carbon atoms are particularly preferable. That is, the most preferable organic acids in this invention are lauric acid having 12 carbon atoms, myristic acid having 14 carbon atoms, palmitic acid having 16 carbon atoms, stearic acid having 18 carbon atoms, arachic acid having 20 carbon atoms and behenic acid having 22 carbon atoms.

In 'this invention,-- further, aliphatic dicarboxylic acids having from 4 to carbon atoms, such as, succinic acid, glutaric acid, adipic acid, sebacic acid, etc., may be used.

The proportion of the above-mentioned reducing agent is generally determined by its reducing power, rate of decomposition by light, molecular Weight and the like, of the compounds to be used. However, in general, it is preferable to use, for one part by weight of the lightinsensitive and reducible silver salt, from to 10 parts by weight of the reducing agent. The proportions of other ingredients are the same as that used in our previous copending U.S. application No. 617,498. That is, these proportions are, respectively, from to )5 part by weight of the light-sensitivity providing material (b), and A to 10 parts by weight of organic acid (c), together with from to parts by weight of a binder.

In the following examples, specific embodiments of this invention and some of the most preferred methods of preparing the thermally developable light-sensitive elements containing the above-mentioned are shown.

EXAMPLES 1-7 In each example, a uniform dispersion was prepared in accordance with the composition as shown in Table 1, and a thermally developable light-sensitive element was produced by applying the dispersion to a photographic paper, such that the dry thickness of the layer formed thereby is 15 microns.

The light-sensitive material thus produced was heated to provide a negative image of an original, after exposing imagewise to a tungsten lamp. When the negative image thus obtained was placed in a light place, the contrast between image areas and background areas of the material was not changed.

On the other hand, when the thermally developable light-sensitive material thus prepared was exposed for 5 minutes to a high-pressure mercury lamp of 400 watts at a distance of 10 cm. from the light source and heated to the extent as shown in the Table, a good positive image of an original was obtained. When the image thus obtained was exposed to white light, the contrast between image of an original areas and background areas of the material was not changed.

sron) 1 Silver behenate (10% methanol) ml Strontium iodide. 6Hz0 (1/[50 N methanol solution In 15 10 10 10 Potassium iodide (1/50 N methanol solution) ml sensitizing dye *1 (0.25%

methanol solution) ml l-ascorbic acid, g... l-aseorbyl palmitate,

l-aseorbyl laurate, g l-ascorbyl myristate, g. Sebacie acid, g Adipic acid, g- Heating time, sec 10 Temperature, C 120 120 1 Monoester. 5 Diester. *1 3-ethyl-543-methyl-2-tl1iazonilidene)-ethylidene) -rhodanine (J. Phys. Chem., 56 1602 (1952)).

EXAMPLES 8-10 Dispersions having the following compositions were applied to photographic paper and dried. The dry thick ness of resulting layer is 15 microns.

TABLE 2 Example number Polyvinyl butyral (10% methanol solution) 60 00 60 Benzotriazolyl silver salt (10% methanol disper- Sion 20 20 20 Silver behenate (10% methanol dispersion)" Strontium iodide (1/50 N methanol solution) 10 10 10 Potassium iodide (1/50 N methanol solution) sensitizing dye* (0.25% methanol solution)- 0. 1 0. 4

Benzoin, g 0.3 Adipie 301d. 2 2 Sebacic acid, g 4

*The same merocyanine dye as the sensitizing dye in Example 1.

When these samples were exposed to a tungsten lamp as in Example 1, good negative images were obtained,

and when they were exposed to a mercury lamp, good positive images were obtained. When the images were exposed to white light, the contrast between image and background was not changed.

While the invention has been particularly shown and described with reference to preferred embodiments therof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein Without departing from the spirit and scope of the invention.

What is claimed is:

1. A thermally developable light-sensitive element comprising a support hearing at least one layer containing (a) a light-insensitive and reducible organic silver salt selected from the group consisting of the silver salt of benzotriazole, the silver salts of a member selected from the group consisting of a halogen-, a methyl-, and a nitro-substituted benzotriazole;

(b) a member selected from the group consisting of a silver halide and an inorganic halide, which forms a light-sensitive silver halide by reaction with said organic silver salt of (a);

(c) a reducing agent, which is decomposed by ultraviolet irradiation,. said reducing agent being selected from the group consisting of l-ascorbic acid, a l-ascorbyl monoester, a l-ascorbyl diester, furoin, benzoin and dihydroxy acetone; and

(d) at least one member selected from the group consisting of aliphatic monocarboxylic acids having from 12 to 22 carbon atoms and aliphatic dicarboxylic acids having from 4 to 10 carbon atoms.

2. The thermally developable light-sensitive element as claimed in Claim 1, wherein said inorganic halide which forms a light-sensitive silver salt is a compound having the general formula MXn, wherein said M represents an ion selected from the group consisting of hydrogen, strontium, cadmium, zinc, tin, chromium, sodium, nickel, magnesium, aluminum antimony gold cobalt mercury, lead, beryllium, and ammonium ions; said X represents a halogen ion; and said It represents the valency of said M.

3. A copying process which comprises exposing a lightsensitive element which is thermally developable, and comprises a support bearing at least one layer containing (a) a light-insensitive and reducible organic silver salt selected from the group consisting of the silver salt of benzo-triazole, the silver salts of a member selected from the group consisting of a halogen-, a methyl-, and a nitro-substituted benzotriazole, the silver salt of saccharin, and silver behenate;

(b) a member selected from the group consisting of a silver halide and an inorganic halide, which forms a light-sensitive silver halide by reaction with said organic silver salt of (a);

(c) a reducing agent, which is decomposed by ultraviolet irradiation, said reducing agent being selected from the group consisting of l-ascorbic acid, a 1- ascorbyl monoester, a l-ascorbyl diester, furoin, benzoin and dihydroxy acetone; and

(d) at least one member selected from the group conisisting of aliphatic monocarboxylic acids having from 12 to 22 carbon atoms and aliphatic dicarboxylic acids having from 4 to 10 carbon atoms, image wise to tungsten light; developing said exposed element by heating and then uniformly exposing said element to ultra-violet irradiation.

8, 4. A copying process which comprises exposing a lightsensitive element which is thermally developable and comprises a support bearing at least one layer containing (a) a light-insensitive and reducible organic silver salt selected from the group consisting of the silver salt of benzo-triazole, the silver salts of a member selected from the group consisting of a halogen-, a methyl-, and a nitro-substituted benzotriazole, the silver salt of saccharin, and silver behenate;

(b) a member selected from the group consisting of a silver halide and an inorganic halide, which forms a light-sensitive silver halide by reaction with said organic silver salt of (a);

(c) a reducing agent, which is decomposed by ultraviolet irradiation, said reducing agent being selected from the group consisting of l-ascorbic acid, a 1- ascorbyl monoester, a l-ascorbyl diester, furoin, benzoin and dihydroxy acetone; and

(d) at least one member selected from the group consisting of aliphatic monocarboxylic acids having from 12 to 22 carbon atoms and aliphatic dicarboxylic acids having from 4 to 10 carbon atoms.

through a transparent original image to ultra-violet irradiation; then uniformly exposing said element to visible light and then developing by heating.

References Cited UNITED STATES PATENTS 3,152,904 10/1964 Sorensen 9695 3,392,020 7/1968 Yutzy et al. 9667 3,429,706 2/1969 Shepard 9695 3,457,075 7/1969 Morgan et al. 9667 RONALD H. SMITH, Primary Examiner M. F. KELLEY, Assistant Examiner US. Cl. X.R.

9666 T, 76 R; 1l736.7 

